New 3-D-printed artery can monitor blockages from the inside

When surgeons replace part of a blood vessel—something they do in 450,000 patients per year in the United States to treat blood clots, coronary disease, stroke damage and more—the grafted vessel is monitored by CT scans, ...

Medical research

First-in-human imaging study shows improved heart attack prediction

Doctors need better ways to detect and monitor heart disease, the leading cause of death in industrialized countries. A team led by Massachusetts General Hospital researchers with support from the National Institute of Biomedical ...

Oncology & Cancer

Scientist designs 'express courier service' for immune cells

Immunotherapy is a promising cancer treatment that uses genetically modified immune cells to fight cancer. It can be used as a primary treatment or in combination with other treatments such as radiation and chemotherapy to ...

Medical research

A simple new blood test for tuberculosis

Testing for tuberculosis is fairly straightforward in most cases, but existing tests don't work for everyone because they require something not everyone, especially kids and people with HIV/AIDS, can do: cough up fluid from ...


Listening in to brain communications, without surgery

Plenty of legitimate science – plus a whole lot of science fiction – discusses ways to "hack the brain." What that really means, most of the time – even in the fictional examples – involves surgery, opening the skull ...

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Electric field

In physics, the space surrounding an electric charge or in the presence of a time-varying magnetic field has a property called an electric field. This electric field exerts a force on other electrically charged objects. The concept of an electric field was introduced by Michael Faraday.

The electric field is a vector field with SI units of newtons per coulomb (N C−1) or, equivalently, volts per metre (V m−1). The SI base units of the electric field are kg·m·s−3·A−1. The strength of the field at a given point is defined as the force that would be exerted on a positive test charge of +1 coulomb placed at that point; the direction of the field is given by the direction of that force. Electric fields contain electrical energy with energy density proportional to the square of the field intensity. The electric field is to charge as gravitational acceleration is to mass and force density is to volume.

A moving charge has not just an electric field but also a magnetic field, and in general the electric and magnetic fields are not completely separate phenomena; what one observer perceives as an electric field, another observer in a different frame of reference perceives as a mixture of electric and magnetic fields. For this reason, one speaks of "electromagnetism" or "electromagnetic fields." In quantum mechanics, disturbances in the electromagnetic fields are called photons, and the energy of photons is quantized.

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